public class MergeTwoLists {
    // leetcode 合并两个有序链表
    // https://leetcode.cn/problems/merge-two-sorted-lists/description/?envType=study-plan-v2&envId=top-100-liked
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        ListNode head = new ListNode();
        ListNode cur = head;
        while (list1 != null && list2 != null) {
            if (list1.val < list2.val) {
                cur.next = list1;
                list1 = list1.next;
            }else {
                cur.next = list2;
                list2 = list2.next;
            }
            cur = cur.next;
        }
        if (list1 != null) cur.next = list1;
        if (list2 != null) cur.next = list2;
        return head.next;
    }
}
